diff --git a/modules/API/src/main/java/com/comphenix/protocol/reflect/cloning/ImmutableDetector.java b/modules/API/src/main/java/com/comphenix/protocol/reflect/cloning/ImmutableDetector.java
index 9083253e..ad81b612 100644
--- a/modules/API/src/main/java/com/comphenix/protocol/reflect/cloning/ImmutableDetector.java
+++ b/modules/API/src/main/java/com/comphenix/protocol/reflect/cloning/ImmutableDetector.java
@@ -96,9 +96,9 @@ public class ImmutableDetector implements Cloner {
 			}
 		}
 
-		if (MinecraftReflection.getBlockClass().isAssignableFrom(type)
-				|| MinecraftReflection.getMinecraftClass("Item").isAssignableFrom(type)
-				|| MinecraftReflection.getMinecraftClass("FluidType").isAssignableFrom(type)) {
+		if (MinecraftReflection.is(MinecraftReflection.getBlockClass(), type)
+				|| MinecraftReflection.is(MinecraftReflection.getItemClass(), type)
+				|| MinecraftReflection.is(MinecraftReflection.getFluidTypeClass(), type)) {
 			return true;
 		}
 
diff --git a/modules/API/src/main/java/com/comphenix/protocol/utility/CachedPackage.java b/modules/API/src/main/java/com/comphenix/protocol/utility/CachedPackage.java
index ec6c1870..6d0bd7ba 100644
--- a/modules/API/src/main/java/com/comphenix/protocol/utility/CachedPackage.java
+++ b/modules/API/src/main/java/com/comphenix/protocol/utility/CachedPackage.java
@@ -17,8 +17,8 @@
 package com.comphenix.protocol.utility;
 
 import java.util.Map;
+import java.util.Optional;
 
-import com.google.common.base.Optional;
 import com.google.common.base.Preconditions;
 import com.google.common.base.Strings;
 import com.google.common.collect.Maps;
@@ -51,7 +51,7 @@ class CachedPackage {
 	 */
 	public void setPackageClass(String className, Class<?> clazz) {
 		if (clazz != null) {
-			cache.put(className, Optional.<Class<?>> of(clazz));
+			cache.put(className, Optional.of(clazz));
 		} else {
 			cache.remove(className);
 		}
@@ -63,32 +63,21 @@ class CachedPackage {
 	 * @return Class object.
 	 * @throws RuntimeException If we are unable to find the given class.
 	 */
-	public Class<?> getPackageClass(String className) {
+	public Optional<Class<?>> getPackageClass(String className) {
 		Preconditions.checkNotNull(className, "className cannot be null!");
 
-		// See if we've already looked it up
-		if (cache.containsKey(className)) {
-			Optional<Class<?>> result = cache.get(className);
-			if (!result.isPresent()) {
-				throw new RuntimeException("Cannot find class " + className);
+		Optional<Class<?>> result = cache.get(className);
+		if (result == null) {
+			try {
+				Class<?> clazz = source.loadClass(combine(packageName, className));
+				result = Optional.ofNullable(clazz);
+				cache.put(className, result);
+			} catch (ClassNotFoundException ex) {
+				cache.put(className, Optional.empty());
 			}
-
-			return result.get();
 		}
 
-		try {
-			// Try looking it up
-			Class<?> clazz = source.loadClass(combine(packageName, className));
-			if (clazz == null) {
-				throw new IllegalArgumentException("Source " + source + " returned null for " + className);
-			}
-
-			cache.put(className, Optional.<Class<?>> of(clazz));
-			return clazz;
-		} catch (ClassNotFoundException ex) {
-			cache.put(className, Optional.<Class<?>> absent());
-			throw new RuntimeException("Cannot find class " + className, ex);
-		}
+		return result;
 	}
 
 	/**
diff --git a/modules/API/src/main/java/com/comphenix/protocol/utility/MinecraftReflection.java b/modules/API/src/main/java/com/comphenix/protocol/utility/MinecraftReflection.java
index 61917260..d83729b9 100644
--- a/modules/API/src/main/java/com/comphenix/protocol/utility/MinecraftReflection.java
+++ b/modules/API/src/main/java/com/comphenix/protocol/utility/MinecraftReflection.java
@@ -428,6 +428,17 @@ public class MinecraftReflection {
 		return clazz.isAssignableFrom(object.getClass());
 	}
 
+	/**
+	 * Equivalent to {@link #is(Class, Object)} but we don't call getClass again
+	 */
+	public static boolean is(Class<?> clazz, Class<?> test) {
+		if (clazz == null || test == null) {
+			return false;
+		}
+
+		return clazz.isAssignableFrom(test);
+	}
+
 	/**
 	 * Determine if a given object is a ChunkPosition.
 	 * @param obj - the object to test.
@@ -1137,6 +1148,14 @@ public class MinecraftReflection {
 		}
 	}
 
+	public static Class<?> getItemClass() {
+		return getNullableNMS("Item");
+	}
+
+	public static Class<?> getFluidTypeClass() {
+		return getNullableNMS("FluidType");
+	}
+
 	/**
 	 * Retrieve the WorldType class.
 	 * @return The WorldType class.
@@ -1985,7 +2004,8 @@ public class MinecraftReflection {
 	public static Class<?> getCraftBukkitClass(String className) {
 		if (craftbukkitPackage == null)
 			craftbukkitPackage = new CachedPackage(getCraftBukkitPackage(), getClassSource());
-		return craftbukkitPackage.getPackageClass(className);
+		return craftbukkitPackage.getPackageClass(className)
+				.orElseThrow(() -> new RuntimeException("Failed to find CraftBukkit class: " + className));
 	}
 	
 	/**
@@ -1997,7 +2017,14 @@ public class MinecraftReflection {
 	public static Class<?> getMinecraftClass(String className) {
 		if (minecraftPackage == null)
 			minecraftPackage = new CachedPackage(getMinecraftPackage(), getClassSource());
-		return minecraftPackage.getPackageClass(className);
+		return minecraftPackage.getPackageClass(className)
+				.orElseThrow(() -> new RuntimeException("Failed to find NMS class: " + className));
+	}
+
+	private static Class<?> getNullableNMS(String className) {
+		if (minecraftPackage == null)
+			minecraftPackage = new CachedPackage(getMinecraftPackage(), getClassSource());
+		return minecraftPackage.getPackageClass(className).orElse(null);
 	}
 
 	/**
@@ -2083,7 +2110,8 @@ public class MinecraftReflection {
 	public static Class<?> getMinecraftLibraryClass(String className) {
 		if (libraryPackage == null)
 			libraryPackage = new CachedPackage("", getClassSource());
-		return libraryPackage.getPackageClass(className);
+		return libraryPackage.getPackageClass(className)
+				.orElseThrow(() -> new RuntimeException("Failed to find class: " + className));
 	}
 
 	/**